Avalanche Forecast
Regions: Sea To Sky.
Watch for signs of instability in wind affected terrain. You may find reactive wind slabs on a variety of aspects as northwest winds relocate recent snow in a reverse loading pattern.
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
Saturday night: Flurries bringing around 3 cm, freezing level 500 m. Light southwest wind below 2000m, strong northwest ridgetop wind.
Sunday: Light flurries bringing a trace of snow. Freezing level 1300 m. Light southwest wind below 2000m, strong west-northwest ridgetop wind.
Monday: 10-20 cm new snow. Freezing level 1300 m. Strong southwesterly winds affecting all elevations.
Tuesday: Flurries. Freezing level 700 m. Light to moderate southwest wind.
Avalanche Summary
Reports from Thursday and Friday show:
- Evidence of the previous natural storm cycle up to size 3 on north to east aspects 1500 to 2000 m.
- Good propagation in explosive triggered storm slabs to size 2 (Thursday).
- Storm/wind slabs have been reactive to human triggers around treeline to size 1.
- Cornices have been very reactive to explosives as well as remote human triggers, size 2-2.5.
Going forward:
- Wind loading patterns will likely reverse with northwest winds, forming reactive wind slabs in new features.
Snowpack Summary
20 cm of recent snow overlies a variety of old surfaces including facets, spotty surface hoar in wind sheltered areas around treeline, a sun crust on steep solar aspects and a rain crust below 1500 m. Upper level wind, having recently shifted northwest is likely transporting the recent snow into wind slabs in a reverse-loading pattern in exposed features at upper elevations. Older wind slabs formed by previous southwest winds may also remain reactive to human triggers.
Another weak layer buried in mid-February is composed of a crust, facets or spotty surface hoar depending on elevation/aspect, and is now down 50-80 cm. There have been no recent avalanches reported on this layer. Large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow, wind and/or a rapid rise in temperature could awaken these deeper weak layers.
The mid and lower snowpack is well settled and strong in most areas.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Minimize your exposure time below cornices.
Avalanche Problems
Wind Slabs
Ongoing upper level wind from the northwest is likely reverse-loading recent snow into reactive wind slabs in atypical terrain features.
Aspects: North, North East, East, South East, South, South West.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2
Cornices
Cornices are large, looming, and require extra caution under the current conditions.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1.5 - 2.5